The syntheses of three antineoplastic natural products, aplysistatin, bruceantin, and cyclo-streptolutylstreptolutine (593A) are under investigation. Aplysistatin has been synthesized using, as the key reaction, a mercuric trifluoroacetate mediated brominative cyclization to establish the bicyclo(5.4.0) ether ring system. Model reactions for generation, alkylation, and protection of alpha-diketones are under study for the bruceantin synthesis. An intramolecular 1,3-dipolar addition of an azido olefin is being examined as a route to 593A.